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1591 Park Road Storwater memo August 9, 2024 City of Chanhassen 1591 Park Road Stormwater Subject to receiving a city compliance letter for hard surface coverage and upon submission of a conditional use permit for a contractor’s yard the property owner was requested to provide the city information on current drainage and storm water patterns and sedimentation control. Per this request the following actions have been taken. Silt fencing and haybales were immediately installed to provide erosion control along the east side of the pond and along the south property line, adjacent to the railroad. An existing condition survey was prepared by Moore engineering in June of 2023. The survey showed: a total impervious area of 64.5%, less than the 70% city standard Identified storm sewer manholes and catch basins Showed topography with general drainage patterns Identified pipe inverts within the northwest corner of the on-site pond Identified outlet on the south side of pond showed that the added pavement for west driveway was less than 5,000 square feet The storm sewer manholes and catch basins were opened to confirm pipe inverts and general direction. As part of the Contractor’s Yard CUP the proposed plan provides the following stormwater changes. Reduction in size of the contractor yard impervious surface area. Adding bituminous curbing around the perimeter of the contractor yard paved area Providing curb cuts to allow for surface drainage of the paved area Proposing a turf reinforcement mat at curb cut to prevent channeling of water runoff Propose to flush/clean existing underground stormwater system Provide options for the repair of pond outlet. As this is in the railroad property coordination efforts will be needed Upon review of the proposed drainage plan determine if current stormwater pond is effectively treating stormwater and identify if improvement measures are needed It is understood that once the contractor yard CUP is approved the parameters of the yard and the conditions for the permit will be established and a more specific drainage plan can be applied.